Polymers such as plastics, elastomers, and thermosets are used in large volumes in a wide range of applications such as walls, ceilings, furniture, floor coverings, fabrics, electronics, vehicles and electrical appliances. Because most polymers are flammable, fire safety is important in each of these applications. Generally, fire safety of polymers can be improved by incorporated therein flame retardants. Flame retardants consist of compounds added to a material to improve the material's ability to withstand fire and heat or to resist combustion. Flame retardants can function in a variety of ways to reduce the risk of fire hazard. In one way, they can raise the ignition temperature. In the other ways, they can reduce the rate of burning, flame spread, or the generation of toxic gases and smoke. Phosphorus flame retardants can reduce flammability of the polymer and reduce the generation of toxic gases and smoke.
There are many different kinds of flame retardants which include alumina trihydrate, magnesium hydroxide, halogenated compounds (e.g., chlorinated, fluorinated and brominated compounds), phosphorus compounds (e.g., phosphate esters), antimony oxide, melamine derivatives, and boric acid and other boron compounds. The worldwide sale of flame retardants was 2.35 billion pounds in 2003. It is predicted that the worldwide sale of flame retardants will increase to 2.82 billion pounds in 2008. Among all flame retardants, the two most common kinds are phosphorus flame retardants and halogenated flame retardants. Because of environmental and health concerns over halogenated flame retardants, many parts of Europe are considering bans on some specific halogenated flame retardants. Therefore, the trend is to restrain the use of the halogenated flame retardants and to migrate to other flame retardants such as phosphorus flame retardants. Some examples of phosphorus flame retardants currently in the market includes phosphate ester type flame retardants such as resorcinol bis(diphenyl phosphate) (RDP), bisphenol A bis(diphenyl phosphate), monomeric aromatic phosphate ester compounds (e.g., triphenyl phosphate and tricresyl phosphate) and the like. In general, resorcinol-based phosphate ester flame retardants such as RDP have some more desirable properties over the bisphenol A-based phosphate ester flame retardants because of the presence of meta-phenylene linkages in the former.
Benzoylresorcinol (BR) has been used in the plastic and polymer industries to protect plastic and polymer materials against the harmful effects of the UV radiation from the sun. However, the use of benzoylresorcinol in flame retardants and their applications in plastics were not realized before. The use of benzoylresorcinol in the synthesis of phosphate ester type flame retardants may improve their UV resistance, thermal stability and possibly hydrolytic stability, in addition to flame retardant properties. In general, existing flame-retardant materials including the phosphorus flame retardants still cannot completely block the combustion of polymers. Therefore, there is a need for new benzoylresorcinol-based phosphate ester type flame retardants that have improved flame retardant properties and perhaps improved UV resistance.